The present invention relates to the general technical field of agricultural machinery and in particular to agricultural machines used to sow seeds. The invention relates to a pneumatic sowing element provided with a reservoir designed to contain seeds, at least one planting device and at least one distribution box delivering the seeds, one-by-one, via a rotary dosing element, wherein the seeds are distributed pneumatically. The invention also relates to a single-seed sowing machine or precision sowing machine equipped with such sowing elements.
Such a sowing machine of single-seed type with sowing elements and with distribution of the seeds pneumatically is known, for example, from documents WO 2011/056138 or US 2008/0264313 . Each sowing element has a distribution box provided with a rotary dosing element in order to deposit the seeds one-by-one in the sowing line at constant spacing. In the majority of sowing machines of this type, such as the MAXIMA (registered trademark) single-seed sowing machine sold by the KUHN Company, for example, distribution is achieved by means of a perforated disk, onto which the seeds are sucked by vacuum. The vacuum is generated by a centralized pneumatic device that supplies all sowing elements of the sowing machine. The air flow is channeled toward each distribution box via more or less long flexible tubes. Knowing that the drops in pressure are proportional to the length of the tube, the air flow delivered to the outer distribution boxes is weaker than the air flow delivered to the distribution boxes close to the center of the sowing machine. To assure optimum pickup of seeds for the outer distribution boxes, the suction pressure must be set to the upper operating range of the pneumatic device.
From document WO 2011/056138 a sowing machine is known with a centralized pneumatic device such as described in the foregoing, wherein part of the air flow delivered to the different distribution boxes is circulated and another part is used to guide the seeds onto the soil.
From document US 2008/0264313 a single-seed sowing machine is known with a first centralized pneumatic device for assuring distribution of seeds into different auxiliary reservoirs, each associated with a sowing element, and a second centralized pneumatic device in the form of a vacuum source for assisting distribution of the seeds at the level of each sowing element.
From document FR 1229027 a single-seed sowing machine is known with a distributor, wherein the type is not described precisely and a pneumatic device generates compressed air, which is used to achieve entrainment of the seeds and ejection thereof toward the soil.
It is also known during sowing to provide the field with parallel non-sowed tracks, which will serve as references for the treatment and/or fertilization machines. To establish these tracks, one or more distributors of the sowing machine are deactivated to avoid crushing the future plants and in particular to avoid wasted sowing effort. The periodicity of these tracks is a function of the width of the sowing machine and of that of the treatment machines, in such a way as to avoid repeated covering and/or absences of products between two successive passes. The operating speed of the pneumatic device remains identical regardless of the number of deactivated distributors.